The present invention discloses a single-wire asynchronous serial interface, and a method for transmitting commands and data through one transmission wire, wherein the transmission wire is capable of transmitting signals of three level states. The disclosed interface comprises a signal level extraction circuit receiving signals transmitted through the wire and outputting logic or functional bits according to the received signals; a clock extraction circuit generating clock signals according to the functional bits, and a memory circuit controlled by the clock signals and storing the logic bits. The disclosed method comprises: using two of the level states to represent logic 0 and, logic 1, and the third of the states as a functional bit; and determining whether a group of signals is a command or data by the existence of a functional bit within the group.